1. Field of the Invention
The present invention relates to a data detecting mechanism for detecting film data on an outer periphery of a DX encoded film magazine.
2. Related Background Art
With a spread of a DX encoded film of nowadays, automatic setting of a film speed or sensitivity is facilitated enough to make it the mainstream. The principle of a structure thereof is that a response of an electric signal is detected from a camera-body-side contact provided on a film magazine and a data record pattern on the outer periphery of the film magazine by making use of an electrical conduction, and the film sensitivity is thus read.
Herein, a conventional DX encoded film data detecting mechanism will be explained with reference to the drawings.
FIG. 1 is a fragmentary perspective view illustrating the conventional DX film data detecting mechanism. Referring to FIG. 1, a flexible printed board 5 is fitted to a plurality of protrusions formed on a holding plate 6, thus locating the printed board 5. Contacts 3 are inserted into a plurality of through-holes formed in a contact holding member 2 enough to protrude from the opposite surface. Coil springs 4 are inserted in unillustrated recessed portions of the contacts 3. These respective members are combined to constitute the conventional data detecting mechanism.
FIG. 2 is a sectional view showing the DX encoded film data detecting mechanism when the magazine is loaded. Referring to FIG. 2, the data detecting mechanism is fixed to a camera body 1 with a screw 8. Further, the contact 3 comes in contact with a film magazine 7.
FIG. 3 is a partial sectional enlarged view showing the contact and a data pattern on the outer periphery of the magazine. As illustrated in FIG. 3, the contact 3 comes in point-contact with the unillustrated data record pattern of the film magazine 7.
FIG. 4 is a fragmentary perspective view illustrating an improved DX encoded film data detecting mechanism in the prior art. Referring to FIG. 4, two rows of through-holes are formed in a contact holding member 12, and the contacts 3 are arrayed 3a, 3b corresponding to the through-holes.
FIG. 5 shows an improvement applied to the conventional contact, wherein collapse working is effected on the contacting surface of the contact 3.
According to the conventional construction described above, an insulating material is interposed between the contact on the side of the camera body and the data record pattern on the outer periphery of the magazine. An oil film or an oxide is adhered to the surface of the contact, resulting in an increase in value of an electric resistance. This leads to such a phenomenon that a film sensitivity is misdetected or undetectable. As illustrated in FIG. 3, the magazine assumes a configuration of circular arc, and, hence, the contact is forced to come in a point-contact with the result that the construction is weak to an external factor.
There has hitherto been taken a method of applying Au plating exhibiting an excellency in terms of the electric characteristic and a chemical stability. However, because of a rise in cost of gold plating of nowadays, it is a general practice to decrease the cost by using, though inferior to Au plating, Ni plating or substitute plating.
According to the prior art, as a countermeasure against the above, the following method has hitherto been taken. Two or more paired contacts are provided on the data record pattern surface of the magazine as shown in FIG. 4, thereby increasing a contacting probability. Alternatively, as illustrated in FIG. 5, the surface of the tip portion of the signal contact member undergoes the collapse working to form a consecutive surface contact area, and a ring-like contact portion is thus obtained.
Referring to FIG. 4, the contacts come in two-point-contact with the magazine data record pattern, thus obtaining the paired contacts. However, a configuration, a size and a arrangement of the contacts with respect to the magazine data record pattern surface within a fixed range are limited. Besides, the configuration of the contact member becomes complicated, resulting in a difficulty of working. In addition, the two-point contacts are disposed with predetermined intervals but are composed of one member, and, therefore, the contact force differs depending on the contact portions 3a and 3b. Besides, there is a factor to cause a disorder in terms of the strengths of the contact forces of the respective contact portions because of the configuration being complicated. Accordingly, there arises a problem in which the contacts are forced to come in unstable contact with the magazine data record pattern surface due to a difference in magnitude of the force quantity between the respective contacts, which is derived from the scatter in terms of the contact force quantities thereof.
Further, referring to FIG. 5, because the collapse workings of the contact surfaces of the contacts are various, there is produced a difference in height of the ring-like contact surface with respect to wall surface of the magazine chamber between the contact surface areas thereof. This conduces to a problem wherein the contact area is conceived as a point contact, i.e., the contacts come in biased-point-contact with the circular-arc outer peripheral surface of the magazine and actually in one-point-contact therewith.